Sound transmitting and sound absorbing construction



y 1933. J. J. SULLIVAN 1,918,149

SOUND TRANSMITTING AND SOUND ABSORBING CONSTRUCTION Filed May 1951 Patented July 11, 1933 PATEN OFFICE JEROME J. SULLIVAN, OF MADISON, WISCONSIN, ASSIGNOR TO F. BURGESS LABORA- TORIES, INC., 01? MADISON, WISCONSIN, A CORPORATION OF DELAWARE SOUND TRANSMITTING AND SOUND ABSORBING CONSTRUCTION Application filed May 8, 1931.

This invention relates to improvements in sound transmiting, gas-pressure wave transmitting and sound deadening constructions. lit contemplates the use of an improved foraminous or perforated metal sheet or other suitable, thin material for transmitting sound or for facing sound-absorbing materials, es pecially such as are used in building construction. This invention is a further development of the perforated sheet facing for sound-absorbing materials described and claimed in the Norris Patent No. 1,726,500,

7 issued August 27, 1929.

@ne object of this invention is to secure an increased light reflecting surface over that possible with ordinary perforated metal or other perforated membranes.

In the structure of 'said Norris patent, a thin, perforated sheet of metal is preferred, the holes being made by the ordinary perforating processes. Such perforated sheet metal, even With a small proportion of the area perforated, does not cut down the soundabsorbing efficiency of the sound-absorbing backing. On the contrary, measurements indicate a slight increase in eflieiency. A perforated sheet of this type, however, has the disadvantage that the light reflection usually is cut down in proportion to the perforated area. This is a factor, since good illumination is often important where acoustical correction is necessary. lln my improved sound transmitting facing a membrane may be perforated and may have open-- ings made in it in such manner that little or none of the material is removed or rendered ineffective for'light reflecting purposes. In general this-is effected by forming openings in the side walls of struck-up areas of the membrane.

The specification is to be read in conjunction with the appended drawing in which:

Figs. 1 to 7 inclusive show membranes with certain portions or areas struck up in different forms, the projecting portions haw ing lateral openings;

Fig. 8 shows one type of my improved membrane in conjunction with a sound-absorbing material;

Fig. 9 is a modification thereof.

Serial No. 535,981.

In Fig. 1, struck-up areas or portions 10 are made by stamping or drawing the membrane 11 as shown, and severing and separating it along two parallel edges 12, 12, thereby forming a lateral opening at each side of each projecting portion. This type of structure in which the struck-up areas are shallow, does not require the removal of any metal and provides two openings in each struck-up area. The portions of the struck-up areas which are not open constitute, in effect, strips of metal which slope downwardly toward and merge at both ends with the face of the sheet or they may have an angular or rectangular formation 13, as shown in Fig. 2.

1n Fi g. 3, areas 14 are struck up as in Fig. 1; however each of such areas has only one lateral opening 15. This is made by the severing and separating of one edge of the struck up area from the balance of the membrane. The projecting portion slopes downwardly toward and merges with the sheet.

In Fig. 4, areas 16 are struck up with vertical or substantially vertical side walls. These areas may be circular as shown, or they may be square, triangular or any suitable shape, depending upon the decorative effect desired. The side walls of such areas may be perforated to form lateral openings 17 as shown.

in Fig. 5, a modification of Fig. 1 is shown. The areas 18 and 19 may be struck up in alternate directions and lateral openings formed, as in Fig. 1.

In Fig.6, channels or corrugations 20 areformed in the membrane, the side walls of these channels having perforations 21 as shown.

In the construction of Fig. 7, the lateral opening is obtained by forming long narrow struck-up areas to thereby form long narrow lateral slits 22. Such a louvre-like structure may be used instead of the structure of Fig. 3, which is especially desirable for facing sound absorbing materials in side walls. When used in side walls the struck-up areas project outwardly and downwardly to prevent water, dust, and other undesirable materails from entering readily and affecting the absorber. The lateral slits 22 may be re- IOI placed by small perforations or other openings.

If the previously described membranes are used for facing sound-absorbing materials, the struck-up, areas may be adjacent the sound-absorbing material as shown in Fig. 8 or they may be on the side of the membrane' opposite to that of the sound-absorbling material. The construction of Fig. 8 is usually preferred, the sound absorbing material 23 thereby being spaced from the membrane 11 by the struck up areas, such for example as the strips 10 in Fig. 1, with openings 12.

Where the membrane is stiff enough and the sound absorbing material is soft and incapable of being supported at spaced intervals without sagging, the membrance may constitute the support-for the sound abs0rbing material, although the latter may be independently supported, as pointed out in said Norris patent previously identified. On the other hand, \where saidsound absorbing material has enough cohesion to be fairly stifi', the membrane, where made of sheet metal or other ductible material, may be made quite thin and may be supported by said sounfd absorbing material instead of constituting the support therefor.

In the form shown in Fig. 8, for example, the sound absorbing material may be in the form of.a pad of the structure of insulating building boards and similar material and the sheet metal or other facingof varying degrees of thinness may be secured thereto "either by cementing or by mechanical fastening devices of various forms.

Fig. 9 illustrates an arrangement whereby the sheet metal may be in the form of metal foil, as disclosed in the pending application of Charles F. Burgess, Serial No. 503,543, filed December 19, 1930. In said Fig. 9 the sound absorbing pad 24 may be of any suitable material. such as disclosed in said Burgess application for example, and may be faced with metal foil 25 having certain areas pressed into said pad 24, said foil being glued to the surface of the pad or interlocked with the fibers of the pad to a greater or less extent, by the operation of forming the struck-. up portions or projections. The form of projection 26, shown in Fix 9, is similar to that shown in Fig. 3, with corresponding openings 27 which, however, may face in different directions. In pressing the metal into the pad the fibers catch the severed edge of the projection to some extent, thereby locking the metal to the pad so that under some conditions the; glue or other adhesive need not be used.

The struck-up portions may have any suit able configuration such as will not result in tearing the metal and Where the projecting portions do not face all in the same direction but in different directions the 'mechanical interlocking is more secure.

The membrane'of this invention may also be used for sound transmitting purposes as for sound-pictures where the entire surface of the sound-transmitting screen must be available for light reflection. It may also be used as a facing for absorbers for other types of gas-pressure waves than soundwaves, for example for absorbing materials used in mufiiers for the exhaust gases of in ternal combustion engines, intakes of air compressors, and so forth.

The. membrane of this invention may be formed into tiles as described in said Norris patent and used in a similar manner. It has the further advantage over the plain perforated metal, when mounted in the preferred manner shown in Fig. 8, that the sound absorbing material is not adjacent the holes and will not be affected by paint applied to the membrane or by water and cleaning compounds used during cleanin operations. The ap earance of the tile a so is not affected y the visibility of the absorber through the perforations and discoloration due to uneven air infiltration or circulation is greatly reduced if not eliminated.

The number of lateral holes in the membrane is governed by several factors such as proper transmission of sound, appearance, light reflection, and the, mechanical limitations of the membrane. It is desirable to have the holes as small as possible but not small enough so that they will be clogged readily by paint or similar surface finishing material improperly applied. It is usually desirable to have the openings cover 0.4% or more of the effective area of the membrane. In general the principles set forth in the Norris patent govern the improved construction of this invention so far as number and size of openings is concerned, these being further limited by the type of opening employed. The struck-up areas preferably should not be deep since the light reflection decreases with the depth of the struck-up area. In general it is desirable to have the struck-up areas less than one-eighth inch deep and preferably less than one-sixteenth inch, this being also one dimensionof the opening.

In a particular construction of the shown in Fig. 1 the closely adj acent struck-up areas were formed in sheet metal of about 26 gauge. The areas were about l/et long and 1/16 wide. The rows were 1/ apart and the struck-up areas in each row 1/4! apart. The metal was struck-up sufliciently so that the lateral openings were shaped like the segment of a circle. The openings were about 5/32" long and 1/32 wide at their greatest width.

The struck-up areas previously'described may be made to simulate hammered finishes.

aeiaiee adjacent shallow struck-up small areas with openings in the side walls thereof.

3. In combination with a sound-absorbing material, a facing comprising a thin stifl' membrane having shallow struck-up areas with openings in the side walls thereof, such areas having at least a portion of their edge portions severed and separated from the balv ance of the membrane to thereby form lateral openings therebetwe'en.

4. In combination with a sound-absorbing material, a thing membrane having shallow struck-up areas with openings in the side walls thereof, such areas having at least a portion of their edges severed and separated from the balance of the membrane to thereby form lateral openings therebetween, said sound-absorbing material being on the side of the membrane having said struck-up areas.

5. In combination with a sound-absorbing material, a metallic sheet having a multiplicity of shallow struck-up small areas with openings in the side walls thereof, said sound-absorbing material being spaced from the balance of said sheet by said struck-up areas, the light reflecting area of the front of said sheet being substantially equal to that of said sheet before the formation of said struck-up areas.

6. In combination with a sound-absorbing material, an adjacent thin stifi membrane having shallow struck-up areas with openings in the side walls thereof, such areas having at least a portion of their edges severed and separated from the balance of the membrane to thereby form lateral openings therebetween, said sound-absorbing material, being on the side of the membrane opposite to that of said struck-up areas.

7 The combination with a pad of soundabsorbing material, of afacing therefor of thin ductile metal having slits therein with the metal adjacent one side of said slits pressed above the surrounding surface forming projections and leaving an opening in a plane substantially at right angles to the plane of said metal.

8. The combination with a pad of soundabsorbing material, of a facing therefor of thin ductile metal having portions pressed out of the plane of the adjacent metal, with openings in said projections in planes substantially at right angles to said first mentioned plane, said facing and said pad adhering to each other.

9. The combination with a pad of soundabsorbing material, of a facing therefor comprising sheet material having slits therein,

each slit having one edge offset substantially perpendicularly to the plane of said sheet material forming a sound passage at an angle to said plane.

In testimony whereof, I have subscribed my name.

JEROME J SULLIVAN. 

